Electrical conductor



(No Model.)

J. A. BARRETT. ELECTRICAL CONDUCTOR.

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UNITED STATES PATENT OEEICE.

JOHN A. BARRETT, OF BROOKLYN, NEV YORK.

ELECTRICAL CONDUCTOR.

SPECIFICATION forming partof Letters Patent No. 424,751, dated April 1, 1890.

Application filed November 6, 1889. Serial No. 329,398. (No model.)

T0 @ZZ whom it may concern.-

Beit known that I, JOHN A..BARRETT, a citi- Zen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Electrical Conductors; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

rlhis invention relates to the manufacture of insulated electrical conductors, being more particularly designed for application to that class which may be termed lead-covered cables. In cables of this character it is important to separate the several conductors by a dielectric of the lowest practicable specific inductive capacity. The separating medium in such cables is usually of a composite character, and, though various methods of manufacture have been proposed, the following method is the most commonly practiced conimercially. The wires which are to form the conductors are severally covered to a prescribed thickness with a wrapping or braid 4or web of cotton or jute or other similar material. These covered conductors are then bunched together in any desired number or arrangement and bound together by a iibrous or meshed wrapping of any convenient nature or material to form the so-called core7 of the cable. The core thus constructed is usually placed in a hot-air chamber for the purpose of expelling the moisture present in the fibrous material. The dry core is then commonly treated with a penetrating bath of heated wax or gum or oil,or with heated compounds of Wax, resintasphalt, or similar materials with oil, for the purpose of iilling the brous structure of the core Where applied with such a material as will to some degree remove its hygroscopic nature and seal it against the subsequent absorption ot moisture. Finally, the cable-core, havingbeen prepared and treated with the sealing material substantially as above described, is furnished with a protecting-covering as nearly as possible impervious to water, in order to preserve the insulating properties of the core, and of such a chemical and mechanical nature as to resist decay and damage from t-he external conditions to which it may be subjected. Atpresent lead pipe is extensively employed as the external impervious protecting-sheath. Various incidental modifications of this process may exist; but the product in all cases is essentially the same. The non-conducting material which separates the several conductors is composed, chiefly, of the brous covering first placed upon the wires and the so called insulating compound or sealing material which has by any of several well -lznown methods been caused to penetrate and fill up to a great extent the pores and interstitial spaces throughout the fibrous material.

I proceed, in the construction of a cable according to my invention, upon different principles from the foregoing. It is well known that dry air very much lower in specific inductive capacity than any of the solids which are generally used as the sealing material in this class of cables, and if the air which is already inclosed can be retained and not expelled by the sealing material in applying the latter the desired reduction in specific inductive capacity will be secured.

There are well-known instances where to meet special conditions, cables have been con structed and used in which dry-cotton-insulated cores have been placed in a sheath. of lead pipe without other iilling than the air which surrounds and penetrates the core, the sealing material being left entirely absent. In these cases the inductive capacit-ybetween the wires is found to be low; but such cores are found in practice to be generally unserviceable, chiefly from the fact that any detect or opening in the protectingsheath, even of a very minute character, renders a considerable length of the core liable tothe intrusion of moisture and the consequent loss of insulating properties. It has also been proposed to introduce at intervals in the lead pipe containing such dry cores plugs or lengths of sealing material for the purpose of confining any damage from access of water or moisture within the limits of the section of cable between two adjacent plugs ot sealing material. I have devised a form of electrical conductor in which. a considerable quantity of air is retained in the insulatingspaces at the saine tune that the sealing ma* ICO terial is applied throughout the entire length` of the cable.

Accordingly my invention consists, primarily, in an electrical conductor so covered with a fibrous or ot-her separating medium as to afford in the covering numerous interstitial air-spaces, around which is placed a nonconducting envelope capable of confining the air in such spaces and of retarding or preventing application of the sealing material from driving out the air originally inelosed within the insulating structure.

The invention further consists in two or more wires made up in a group, each wire being covered with fibrous or meshed material containing air, with a non-conducting envelope surrounding the group, capable of retarding or preventing the expulsion of the air by the sealing material when it is applied in the manufacture of the cable.

The invention further consists in a cable in which are assembled the individual conductors or groups of conductors independently covered, as above described, by a fibrous, meshed, or honeycombed coveringsurrounded by a non-conductingenvelope, whether or not an external armor of leader other material is employed.

- moditication.

of a bunched cable, showing anumber of separate wires, each insulated according to my invention and all laid into a bunch and an external covering of moisture-proof material. Fig. 6 is a section showing a pair of air-spaced wires having a single moisture-proof sheath. Fig. 7 is a transverse section showing a cable composed of a number of pairs of wires, each pair being arranged and insulated as shown at Fig. G.

In Figs. l, 2, and 3 I have shown common methods by which the conductor maybe surrounded by iibrous or in eshed material in such manner as to embody with it a considerable proportion of air, together with a non-conducting envelope capable of preventing the sealing material when applied from expelling the air contained within the fibrous or meshed structure. In Fig. l, ais the conductor, b and b are double layers of the iibrous material wrapped thereon, and c is a spirally-applicd tape of non-conductin g material of such a nature--paper, for instance-as to prevent or retard the free penetration of the sealing material. In Fig. 2 the conductor a has the braided covering l), surrounded by the abovedescribed tape et non-conducting material c. In Fig. 3 a single wrapping Z) is used.

In the transverse section, Fig. et, the conductor a is shown surrounded by a covering t) of fibrous or meshed material and inelosed by an envelope of non-conducting materiale, to which thcsealingmaterial has been applied externally.

d., between which and the cable structure is placed the filling of sealing material e, so that. the latter surrounds individually all the wires ofthe core without penetrating i nto the fibrous covering of eachconductor.

Fig. 6 shows a group of two wires a, each having the 'fibrous air-containing covering b and the envelope c, of non-conducting material, surrounding the group, to which the sealing material may be applied.

Fig. 7 shows a telephone-cable made up of groups, each composed of two wires arranged as described with reference to Fig. (3.

In carrying my invention into practical effeet I prefer, first, to serve the wire with a hard cord, strip, or string of non-conducting material, preferably ol low hygroscopic quality, in whatever man ner and to whatever thickness may be required for the particular purpose to which the conductor is to bcv devoted, provided only that a suilicient volume of air is embodied with this covering, and I wrap about this one or more thicknesses of a close covering-such, for instance, as paperso as to give the whole structure the requisite smoothness and roundness, and to prevent the sealing material--such as oil, wax, gum, rubber, gutta-percha, or other material or compound-from penetrating in such a manner as to drive out the air from the interior spaces when such substances are applied to the structure for the purpose of insulating and protecting the interior from the admission of moisture.

I claim as my inventionl. In electric cables of that cla-ss in which the conductor is surrounded by a non-conducting covering and a sealing or filling material, the combination of an electrical conductoig'a fibrous or meshed air-containing covering for the same, a surrounding. non-conducting envelope adapted to continue the contained air, and a sealing material applied to the exterior of the envelope.

2. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or filling material, the combination of two'or more electrieal conductors, each surrounded bya iibrous or meshed air-containin g covering, a non-conducting envelope surrounding the group of such wires and adapted to confine the contained air, and a sealing material applied to the exterior of the envelope.

3. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or filling material, a cable consisting of a group of electrical conductors, each of which is surrounded, tirst, by a fibrous or meshed air-containing covering', and, second, by a non-conducting envelope adapted to coniine the contained IOO IIO

. air, and a sealing material applied to the exterior of each one of the groups constituting the cable.

4. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or filling material, a cable composed of separate groups, each group containing two or more Wires, each wire surrounded by a fibrous or meshed aircontaining covering, and each group of Wires surrounded by a non-conducting envelope adapted to confine the contained air, and a sealing material applied to the exterior of each group of wires constituting the cable.

5. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or filling material, the combination of a group of electrical conductors, each surrounded by a fibrous or meshed air-containing covering, a non-conducting envelope surrounding the group of such Wires and adapted to confine the contained air, a sealing material applied to the exterior of the envelope, and a surrounding sheath of lead.

6. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or filling inaterial, a cable consisting of a group of electrical conductors, each of which is surrounded, irst, by a fibrous or meshed air-containing covering, and, second, by a non-conducting envelope adapted to confine the contained air, a sealing material applied to the exterioil of the envelope of each of the Wires constituting the cable, and a surrounding sheath of lead.

7. In electric cables of that class in which the conductor is surrounded by a non-conducting covering and a sealing or iilling inaterial, a cable composed of separate groups, each group containingtwo or more Wires, each Wire surrounded by a fibrous or meshed aircontaining covering, and each group of wires surrounded by a non-conducting envelope adapted to confine the contained air, a sealing material applied to the exterior of the envelope of each group of wires constituting the cable, and a sheath of lead surrounding the core thus constructed.

In testimony Whereot` I aiiix my signature in presence of two Witnesses.

JOHN A. BARRETT.

Witnesses:

FERNANDO SOLINGER, O. F. HIBBARD. 

